Iron deficiency in cannabis plants

How to Spot and Correct an Iron Deficiency in Cannabis Plants

Welcome to the diagnostic lab with Dr. Organitek. Today we will take a look at Iron deficiency in cannabis plants, what it looks like, and how to fix it.

The cannabis plant is a complicated creature and just like us, it needs a well-rounded diet to maintain its health. One of the essential nutrients that often gets overlooked in cannabis cultivation is Iron. Iron doesn’t get as much attention as the big 3 in N-K-P or Nitrogen, Potassium, and Phosphorous so it’s easy to misdiagnose a deficiency by overlooking Iron.

Iron deficiency in cannabis plants
Interveinal chlorosis with pale white color and browning on leaf margins

(Fe) Iron: Important in chlorophyll formation, helps in the respiration of sugars to provide growth.

Deficiency: Iron deficiency is common and causes new growth to become pale and blossoms to drop from the plant. Yellowing is initially observed between the veins and leaves may die along their margins.

Toxicity: Excessive Iron is difficult to spot and is very rare and likely not an issue.

Micronutrient: Absorbed in small to minute quantities. They are generally less well known than the macronutrients since most plant foods don’t contain them.

What Does Iron Do for Cannabis Plants?

Iron plays a role in the chlorophyll production of the cannabis plant so it is essential for photosynthesis where the plant turns light into energy. It also helps with respiration and metabolism where it acts as a catalyst for enzymatic reactions that drive growth and development in the root zone, foliage, and flowers.

An iron deficiency in cannabis plants leads to weak growth and poor yield and can drastically impact the plant’s vitality making it look weak with signs of yellow leaves.

What Are the Symptoms of Iron Deficiency?

Iron deficiencies come in 3 stages and the earlier you diagnose it, the sooner you can start to treat and correct it. Early detection is important because, in the later stages, the plant may be so damaged that it will affect the quality of the flower.

The Early Stage of an Iron Deficiency

In the early stages of an Iron deficiency, your plants will start showing yellowing between the leaf veins, primarily on younger leaves and new growth. This symptom is known as interveinal chlorosis and it is easy to misdiagnose it because of its similarity to nitrogen deficiency but more pale and whiteish in color.

The Progression of an Iron Deficiency

As Iron deficiency progresses, the yellowing extends throughout the whole leaf, and the plant’s growth slows down. It’s very noticeable in the vegetative stage when you would expect explosive growth.

Another telltale sign that your plants have lack of Iron is if the leaves start to turn white. In cases of severe Iron deficiency, it will almost look like the plant has seen a ghost.

The Late Stage of an Iron Deficiency

In the late stages of Iron deficiency, leaves turn almost completely white or yellow and may show some browning at the tips. You will notice severely stunted growth and if left untreated, your plants will start losing leaves, and the yield will reduce drastically.

Iron deficiency in cannabis plants progression
The progression of Iron deficiency in cannabis

What Causes a Cannabis Iron Deficiency and What Are Common Misdiagnoses?

There’s a Sherlock Holmes level of detective work involved in correctly diagnosing an Iron deficiency in the very early stages. Interveinal chlorosis is common to many cannabis nutrient deficiencies so don’t jump to any conclusions based on that alone.

It’s crucial to understand that Iron deficiency symptoms in plants can mimic other nutrient deficiencies like phosphorus or potassium deficiency, or even issues like nutrient lockout. If you start seeing white leaves on the marijuana plant you can be almost certain that you are dealing with an Iron issue.

Various factors can cause a deficiency of Iron in plants, including pH imbalances, poor soil quality, lack of Iron in the potting mix, or nutrient lockout due to excess salts and other minerals which prevents the absorption of Iron.

How to Fix a Cannabis Iron Deficiency

If you recognize the symptoms and diagnose your plants with an Iron deficiency, you need to act quickly to increase the amount of Iron in the growing medium. If you act quickly and perform the steps below, you will start seeing your plant grow back to health in 10-14 days.

Already damaged growth won’t recover but new growth will start showing signs of improvement fairly quickly.

  1. Check the pH level – Iron is best absorbed in soil with a pH of 6.0 – 6.5 and in hydro or soilless mediums with a pH of 5.5 – 6.5. Make sure your pH is in the right range to facilitate Iron absorption.
  2. Inspect your soil and water – Poor drainage or waterlogged soil can contribute to Iron deficiency so make sure your plants are getting the right amount of water and that the soil allows proper drainage.
  3. Use Iron chelates – Applying chelated Iron can help the plant absorb Iron more efficiently.
  4. Flush the growing medium – As a last resort you may need to flush the growing medium completely with clean pH water to remove excess nutrients and reapply a balanced nutrient solution. This is how you perform a flush.
  5. Switch to Iron-rich nutrients – Iron-rich nutrients can supplement your plants with the necessary Iron.
  6. Excessive micronutrients – An excess of Zinc, Copper, or Manganese can reduce the availability of Iron so in rare cases, a toxicity in those micronutrients can be the culprit.

Learn how to spot and fix cannabis nutrient deficiencies

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